package NC69_链表中倒数最后k个结点;

import java.util.Stack;

class ListNode {
    int val;
    ListNode next = null;

    public ListNode(int val) {
        this.val = val;
    }
}

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param pHead ListNode类
     * @param k int整型
     * @return ListNode类
     */
    public ListNode FindKthToTail (ListNode pHead, int k) {
        // write code here
        if (pHead == null || k == 0){
            return null;
        }

        Stack<ListNode> stack = new Stack<>();
        while (pHead != null){
            stack.push(pHead);
            pHead = pHead.next;
        }

        // 判断栈的元素个数是否少于 k
        if (stack.size() < k){
            return null;
        }

        ListNode node = null;
        while (k-- > 0){
            node = stack.pop();
        }
        return node;
    }
}